Ideally______for Broadway theatres and Firth Avenue, the AVw York Park hotel is n favounte with many guests.

A. locating                   B. being located            C. having been located  D. located

It has been proved______eating vegetables in childhood helps to protect you against serious illnesses in later life.

A. if                            B. because                   C. when                             D. that

Something as simple as______some cold water may clear your mind and relieve pressure.

A. to drink                   B. drinking                   C to be drinking       D. drunk

As his best friend. I can make accurate guesses about______he will do or think.

A. what                       B. which                      C. whom                     D. that

If there's a lot of work______. I'm happy to just keep on until it is finished.

A. to do                  B. to be doing             C. done                  D. doing

In recent years many football clubs______as business to make a profit.

A. have run               B. have been run         C had been run          D. will run

― Are you ready for Spain?

― Yes. 1 want the girls to experience that______they are young.

A. while                B. until                  C. if                     D. before

My sister, an inexperienced rider, was found sitting on the bicycle______to balance it.

A. having tried               B. trying                    C. to try                         D. tried

2．如圖17所示，將質(zhì)量M=1.20 kg的小沙箱，用輕質(zhì)軟繩（不可伸長(zhǎng)）懸掛起來，開始處于靜止?fàn)顟B(tài)，繩的長(zhǎng)度l=0.80 m。用槍向沙箱發(fā)射質(zhì)量m=0.05 kg的子彈，子彈以v₀=100 m/s 的速度向右水平擊中小沙箱，并留在小砂箱中，小沙箱沿豎直面向上擺動(dòng)。假設(shè)沙箱每次向左運(yùn)動(dòng)到最低點(diǎn)時(shí)就恰好有一顆同樣速度的子彈射入沙箱，子彈射入沙箱的過程時(shí)間極短，可忽略不計(jì)，重力加速度g取10 m/s²，不計(jì)空氣阻力。

   （1）求第一顆子彈射入沙箱的過程中子彈對(duì)砂箱的沖量大小；

   （2）求第一顆子彈射入沙箱并相對(duì)沙箱靜止的瞬間，求砂箱對(duì)繩的拉力的大��；

   （3）求第一顆子彈射入沙箱后，砂箱擺動(dòng)的最大高度；

   （4）要使沙箱擺動(dòng)的最大角度小于60°，射入沙箱的子彈數(shù)目至少為多少

According to the air traffic rules, you______switch off your mobile phone before bearding.

A. may                        B. can                          C. would                     D. should